The aim of this project is to develop systems for measuring the frequency of point mutations and DNA change in male germinal tissue. These systems would have the advantages of testing the human population by means of readily available samples, i.e., spermatozoa. At present enzyme histochemical methods are being developed to detect point mutations in male mice. The histochemical staining technique has been quantatized for alpha-glycerophosphate dehydrogenase and succinyl dehydrogenase. Preliminary work has started with the Axiomat scanning microscope to determine its usefulness in measuring the distribution of DNA content in a population of sperm. It is hoped that this instrument may prove useful in showing changes in the distribution pattern in sperm populations derived from mice treated or untreated with known mutagens.